1. Field of the Invention
This invention relates to a recording and/or reproducing apparatus in which a disc cartridge having a disc-shaped recording medium for writing and/or reading information signals accommodated in a cartridge proper is loaded and in which recording and/or reproduction of the information signals is effected on or from the recording medium in the disc cartridge. More particularly, it relates to a recording and/or reproducing apparatus provided with a temperature sensor for sensing the temperature of a disc cartridge loaded therein, and to a disc cartridge loaded into a recording and/or reproducing apparatus for sensing the temperature of a recording medium accommodated within a cartridge proper.
2. Description of the Prior Art
In a recording medium adapted for recording and/or reproducing information signals by magnetic, optical or photomagnetic means, the temperature of the recording medium during writing or reading is crucial since it influences recording and reproduction significantly.
In the case of a magneto-optical disc, for example, a high laser power is required during recording or erasure because the temperature of a magnetic thin film needs to be raised to higher than a Curie temperature, while a lower laser power is required during reproduction for which the recorded information is not demagnetized. These laser powers need to be determined as a function of the temperature of the recording medium that is, it needs to be set to a value which will allow for optimum recording or reproduction of information signals. For example, it may occur that, even if the recording laser power is set to an optimum value for a certain temperature of the recording medium, the recording laser power may become too high or too low due to changes in the recording medium temperature, such that the direction of magnetization cannot be inverted satisfactorily. Similarly, if the laser power during the reproduction or erasure is too high or too low, it may occur that the recorded information signals are demagnetized or are not erased completely.
The conventional practice for sensing the temperature of the recording medium is to provide the cartridge proper with a small orifice through which the recording medium temperature is sensed by means of a radiation thermometer provided in the recording and/or reproducing apparatus to permit a laser to be radiated at an optimum laser power as a function of temperature changes of the recording medium.
However, in this case, fine dust and dirt may intruded through the orifice into the inside of the cartridge to cause errors in information signals to which interfere with recording or reproduction. Although the orifice may be stopped when not in use, it becomes necessary to provide a member for stopping the orifice and means for permitting the sliding of the member, as well as driving means for sliding the member on the recording and/or apparatus, resulting in an increased number of component items and increased costs. On the other hand, the temperature of an order of 30.degree. to 40.degree. C. cannot be measured accurately with a radiation thermometer.
There has also been proposed by the Japanese Patent KOKAI Publication No. 1-191329(1989) an arrangement in which a temperature sensor for sensing the temperature of a recording medium is mounted integrally on an optical head and adapted to be moved therewith radially of the recording medium for sensing the temperature of the recording medium.
However, in this case, the temperature of the recording medium can not be measured accurately by reason of a gap between the temperature sensor and the recording medium. Thus a laser beam cannot be irradiated at an optimum laser power as a function of the prevailing temperature of the recording medium, so that information signals cannot be recorded satisfactorily.